Transformer construction and method of making the same



May 22, 1934., F s SMH-'H 1,960,033

TRANSFORMER CONSTRUCTION AND METHOD OF' MAKING THE SAME BY ATTQRNEYS04W# MVM lMay 22, 1%34. v s SMH-H 1960,033

TRANSFORMER CONSTRUCTION AND METHOD 0F MAKING THE SAME Fild Dec. 5, 19312 Sheets-Sheet 2 b 2f l 4 0 /3 22a, /8 2/3 sNvENToR :ff 'M BY ATTORNEY5@far-44m Patented May 22, l934 hill D STATESv rarest' orries ETRANSFRBERC N S T E U C T E O N AND ll/ETHGD 0F MAKING THE SAME 11 Claims.

This invention relates to transformer construction, and moreparticularly to a nigh volt age transformer construction.

One of the objects of this invention to provide a transformer which iscompact in form, rugged in construction, and efficient in operau tion.Another object is to provide a transformer construction which iseconomical to produce and simple and rapid to manufacture. Anotherobject of this inventlon is to provide a transformer of the.above-mentioned character which is well adapted to function at highpotentials and in which the possibility of internal breakdown is greatlyreduced without saorice of other important advantages. Another object isto provide a transformer construction in which high insulation isachieved with the use of a minimum amount of insulating material andmore particularly to provide a winding construction in which effectiveinsulation and particularly graded in sulation may be achieved ininexpensive, and thoroughly dependable Way, Another object is to providea transformer winding construction adapted to function high voltages inwhich highly efficient use is made of the availm able winding space inorder thus to minimize thr` length oi the magnetic circuit and thus toachieve better linkage, better regulation, and higher eiicienc-y. Otherobjects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists the features of construction, comiinations of elements, arrangements of parts and in several steps andrelation and order of each of the saine to one or more of the others,all will be illustratively described herein, and the scope of theapplication of which will indicated in vthe following claims.

ln the accom drawings, in which is shown one of the various possibleembodiments of my invention,

Figure i is a vertical central sectional View cfa completelynbledtransforrner;

Figure 2 is an enlarged fragmentary sectional view of the windings shownin Figure l;

Figure 3 an isometric view, partly in section, of one of the coilspacers of Figures l and 2, and

Figure l is a horizontal central sectional View of the transformer buton a reduced scale, certain parts boing omitted, showing how the core istted with the casing.

Similar reference characters refer to similar parts throughout theseveral views in the drawings.

Referring to the drawings and more particularly to Figure 1, firstprovide a container 10, preferably in the form of a cylindrical steeltank capable of withstanding appreciable pressures. One end il of thetank is preferably made integral with the main body portion thereofwhile the other open end is closed by a closure or shell 12 after theapparatus has been inserted therein; the manner of securing the closure12 in place will be more clearly described hereinafter.

Within the cylindrical tank 1i) is the transe former construction whichincludes a suitable iron core; the latter illustratively is of the shelltype, as isrbetter seen from Figure fi in which the core is generallyindicated at 13. The core has a central leg l about which the windingsextend and it has side legs 13a and 13b joined by crossmeinbers 13C and13d. The laminations of which the core 13 is built up are held togetherby suitable structural steel members preferably of angie cross-sectionand may include pairs of angle members 16 and 1'7 extending crosswiseor" the leg 13d and clamped together as by bolts 18; and pairs of anglemembers 19 and 20 which with, the aid of bolts 2i clamp the right-handend of the core l13 together (see Figures l and 4).

Extending `lengthwise of the outer core legs i3a and 13b are anglemembers 22 and 23 in pairs, the pair of which, by the aid of `bolts 18and 24 clamp the laminations of the side core legs 13a and. 13b securelytogether. 85

These angle members 22 and 23 extend to the right beyond the core '13(see Figure 4) where they engage the bottom 11 of the container 10.After the core structure with the windingthereon has been assembled andclamped together and inserted into the tank 10, as shown in Figure 4,the closure 12 is inserted into the left-hand open end of the containerto rest against the lefthand end of the core 13; thereupon, theperipheral portions of the casing 10 are bent over as at 10iL onto theclosure 12 and Welded thereto as at 25, thus form-ing a seal.

About the middle leg of the transformer core i3 (see Figures l and 2) isa tube-like member 26 of solid dielectric material, such as phenoliccondensation product, and upon the member 26 and lengthwise thereof iswound the low potential winding 27, illustratively shown in the drawingsas comprising relatively heavy wire wound in two layers. The terminalends of the winding 23 (see now Figure l) are led by suitable conductors28 and 29 to the connecting terminals 30 and 31 thatare led to theexterior of the casing 10 through a suitable insulating bushing 32 ofany desired construction and in sealed or gas-tight connection with thewall of the container. Conveniently the low voltage terminals may be ledthrough the bottom wall 11 of the tank. Thus, low voltage energy may beled to or from the low voltage winding of the transformer.

Fitted onto the middle leg 15 of the core (see Figure 1) and adjacentthe ends thereof are two spiders 33 and 34 which support a tube-likeinember of solid dielectric material such as phenolic condensationproduct, member 35 being of materially larger diameter than the outsidediameter of the low voltage winding 27 so that, together with the spacesbetween the spokes of the spiders 33 and 34, a suitable dielectric andcooling medium, a preferred form of which is hereinafter described, mayfreely circulate therethrough.

Considering now the construction of the high voltage winding, it mayiirst be noted that the sleeve 35, with certain solid dielectric parts.hereinafter described mounted thereon, may be mounted in any suitableway in a lathe or winding machine for rotation so that the windings maybe wound thereon. A plurality of spacers of solid dielectric material isrst placed upon the sleeve 35 and in Figure 1 I have shown, by way ofillustration, five such spacers; they are indicated at 36, 37, 38, 39and 60 in Figure 1, and inasmuch as their construction is similar itwill suflice to describe one of them in detail. Accordingly, referencemay now be made to Figure 3 of the drawings.

In Figure 3 one of these spacers, for example spacer 37, is shown inperspective and in crosssection. It includes a hub 40 whose insidediameter is equivalent to the outside diameter of the sleeve 35 whichcarries the spacers and projecting peripherally from the hub 40 are twoflanges 41 and 42 whose outer faces 41a and 42n extend preferably atright angles to the axis of the spacer while the inner faces 4lb and 42bmay be inclined so as substantially to taper the flanges incross-section, thus to give them greater mechanical strength andrigidity (see also Figure 2).

Flange 41 terminates flush with the left-hand end of the hub 40, asviewed in Figure 3, while the hub 40 projects beyond or to the right, asviewed in Figure 3, of the other flange 42 to form an extension orshoulder 40a.

Extending in agiven plane lengthwise of the axis of the spacer 37 andinclined as is better shown in Figure 3 are two alined holes 45 and 46in the anges 42 and 41 respectively.

The various spacers 36, 37, 38, 39 and 60 are slipped onto the sleeve 35substantially in the relation shown in Figure 1 with the extendedportions 40a of the hubs 40 directed in the same direction; the spacersare preferably equally spaced from one another and may be held in placeby any suitable means, s uch as by pins or pegs of solid dielectricmaterial indicated at 44 (Figure 1) that extend preferably through thatpart of the hub 40 that is between the flanges 41 and 42 and into thesolid dielectric sleeve 35.

This assemblage, suitably mounted to be rotated, is now ready for thereception of the windings. I may employ any suitable insulated wire forbuilding up the high tension winding and 'this is first threaded throughthe holes 45-46 in the flanges 41-42 of the endmost spacer 36 (see.Figure l) and the space between spacer 36 and spacci' 37 filled up withwire to form a coil 47, the winding proceeding as is hereinafter moreclearly described; the end of the coil 47 is then threaded through thehole 45 in the flange 42 of spacer 37 and, after leaving a short length,is cut off.

rPhe end of the supply of wii'e is then threaded through the hole 45 inthe flange 41 of spacer 37 and the space between the latter and spacer38 filled up with wire to form the coil 48. These steps are thenrepeated to form coils 49 and 50.

Considering now how these individual coils are wound, reference shouldfirst be made to Figure 2 in which coil 50, between spacers 39 and 60,is shown in enlarged cross-section and in completed form the conductoror wire is wound into a bottoni layer 5l directly onto the sleeve 35 andbetween the :dange 41 of spacer 39 and the extension 4()a of the hub 40.

Then there is wrapped around the layer 50 suitable solid dielectricmaterial, such as paper, but this solid dielectric material is graded;for example, it may include a single layer 52 that extends entirelyacross the wire layer 51 and an additional layer of solid dielectricindicated at 53 that extends only part way, for example half way. Thelayers 52 and 53 may be of a suitable paper, for example. Winding layer5l. was wound in a direction from the right to the left, as viewed inFigure 2, and now a second layer of wire indicated at 54 is wound on topof the insulation 52-53 but it is wound in a direction from the left tothe right. With respect to the two layers of wire 51 and 54, therelative voltage iierence increases in a direction from the left to theright, as will be clear from the direction in which the layers are builtup, but the graded insulation, preferably and conveniently in the formof layers of sheet material of different widths, achieves commensuratelyand substantially proportionately graded insulation between the twolayers of wire.

The above process is repeated until the wind- .has progressed to athickness equal to the thickness of the hub extension 40a, whence thesesteps of winding of the layers of wire with interposed graded insulationproceeds further but now the winding layers and the layers of interposedinsulation extend between the face 42@ of the flange 42 of spacer 60 andthe face 41n of the spacer 39, the winding and insulation thus Textending also above and around the hub extension 40e. In each instanceadjacent layers of the winding are separated by graded insulation. Whenthe winding 50 has been completed, its free end is passed through thehole 45 in the flange 42 and into the space between the flanges 41 and42 of the spacer 6U.

The coils 47, 48, 49 and 50 having thus been completed, the coil ends ofadjacent coils, projecting through the holes in the flanges of thespacers, may be connected together as at 55 by soldering or otherwise,the connections being accommodated in the space between the flanges ofthe individual spacers,

Certain coactions of this construction with e other features of myinvention are pointed out in detail hereinafter.

The ends of the high voltage winding Ythus achieved by the seriallyconnected coil sections may be connected in any suitable manner tosuitable terminals or the like so that high voltage energy may be led toor down from the high voltage winding. Illustratively, the terminal endof coil 47 may be led by conductor 56 and grounded to the tank or casing10 at any suitable point, for examplaas is diagrammatically indicated at57, But there may be instances where it is desirable to employ buffercoils and as illustrative of how, by way of certain features of myinvention, I meet even this requirement 15G in a simple and thoroughlypractical manner. I have shown the left-hand terminus of coil (Figures 1and 2) connected as at 58, in the space between the flanges 41 and 42 ofthe spacer 60 to the end 59 of a buffer winding 61, preferably of aheavier insulated wire or conductor of any suitable character, that iswound into the spacing between the flanges 42 and 41 of an additionalspacer member 62 which is mounted on the insulating sleeve 35 butreversed end for end so that its flange 41 abuts face to face againstthe flange 41 of the spacer 60, whereby the passages 46 through thesefianges become positioned adjacent cne another to form a V-shapedchannel or passage (see Figure 2) through which the end 59 of the buiferwinding 61 may be passed for connection as at 58 to the end of thewinding 50.

The buffer winding 61 may be wound at the completion of the winding ofthe other coils as above described and the turns or layers thereof maybe insulated from each other in any desired or suitable way. The endterminal 63 of the buffer winding 61 is led by a conductor 64 throughthe wall of the casing 10 by means of any suitable insulated bushing orhigh voltage erminal construction generally indicated at 65 in Figure 1.

The casing 10 is lled with a gaseous dielectric under pressure on theorder of fifteen atmospheres; this gas may comprise nitrogen or, by wayof further example, a mixture of nitrogen and helium where better heatdissipation is required. This gaseous dielectric under pressure bringsabout certain unique and advantageous coactions with the features abovedescribed.

For example, it fills the space between the low voltage winding 27 andthe insulating sleeve 35 which supports the high voltage coils and is inseries with the solid dielectric of the tube 35 and thus makes possible,by reason of the distribution of the dielectric stress between the soliddielectric (whose permittivity may be as high as 5) and the gaseousdielectric under pressure (whose permittivity is unity) inversely as thepermittivities of the two media, a much closer spacing between the hightension winding and the low tension winding than wouldbe otherwisepossible.

But by reason of the features of construction embodied in the soliddielectric spacers which may be made of phenolic condensation productand thus easily molded, I am enabled to accommodate, for a givenover-all length of high voltage winding, many more turns than wouldotherwise be possible. This feature is important in that it makespossible the use of a shorter magnetic circuit, achieves closer linkagebetween the magnetic circuit and the windings, achieves betterregulation of the transformer, and makes for higher efficiency, lesscost of construction, and greatly reduced weight of the resultantconstruction.

To better understand this feature, it might rst be pointed out that theindividual coils have to be solidly supported mechanically because theyare sometimes subjected to substantial mechanical forces resulting fromthe electrical reactions that might take place, and it is therefore animportant advantage if the coils themselves together with soliddielectric material, such as the hubs 40 with the extensions 40a, arearranged so that they solidly back one another up and support each otheragainst axial movement. The axial length of the hub portions 40-40a (seeFigure 1) must therefore be sufficient to provide adequate soliddielectric material between the inner layers of one winding and theinner layers of the adjacent winding in order to insulate thesesatisfactorily from one another,

But the outer layers of adjacent coils are insulated from each other, inan axial direction, not by solid dielectric alone but by a compositedielectric which includes serially related solid dielectric material(anges 41 or 42) of relatively high permittivity and the seriallyrelated gaseous dielectric under pressure, of unity permittivity, thatintervenes the anges of the individual spacers.

Because of the inverse distribution of the di electric stress betweenthese serially related dielectrics of such vastly diiferentpermittivities, the spacing between the outer layers of adjacent coilscan be made much less than the spacing between the inner layers whichare mechanically separated by solid dielectric material alone, and thusI am enabled to gain considerably in space, for the windingthat wouldotherwise-be occupied by solid dielectric material. In the aggregate andin the illustrative embodiment abovedescribed, and shown in thedrawings, a high percentage of gain in winding space is thus achieved.

Furthermore, the outside conguration of the spacers insures that thesurface leakage path between adjacent coils is relatively long but inthis connection it is to be pointed out that the gaseous dielectricunder pressure in exceedingly great measure minimizes surface leakage byits coaction with the solid dielectric along the surface of whichleakage might otherwise take place.

This coaction of the gaseous dielectric under pressure in so greatlyminimizing surface leakage furthermore makes it possible for me toprovide hub portions on the spacers of an axial length that takes lintoaccount mainly only the direct dielectric stress toewhich the hubportion is subjected by the parts which it directly insulates, inasmuchas the gaseous dielectric under pressure, coacting with and permeatingto all of the surfaces of the solid dielectric vmaterial employed sogreatly cuts down the possibility of surface leakage that increase inlength on account of the latter factor is hardly necessary. Thus, I amenabled to achieve still further compactness of construction andminimization of solid dielectric material employed, the space occupiedby solid dielectric material that would otherwise be necessary beingthus utilized by the winding. l

The gaseous dielectric under pressure, having a very high dielectricstrength, moreover coacts in a unique way with the paper insulation52-53 (see Figure 2) that is interposed between thev layers of thecoils, where paper is thus employed. It is sorbed by the paperdielectric and occupies the spaces that exist between the fibers of thepaper insulation and between the latter and the adjacent layers of wire.Such spaces, if filled with air orother gaseous dielectric atatmospheric pressure, would be over-stressed, due to dielectric fluxrefraction and due to the unequal voltage distribution acrossdielectrics of unlike permittivities (air and paper) in series multiple.For example, the permittivity of the paper is on the order Yof 3 or 4and the permittivity of the air is about unity. The air at atmosphericpressure, a weak dielectric, would thus be made to assume three or fourtimes the stress assumed by the paper and would rapidly break down andcause puncture. However, such possible air spaces in accordance withcertain features of my invention, are lled with the gas under pressureon the order of fifteen atmospheres and hence one whose dielectricstrength is many times that of air at atmospheric pressure. The sameabovementioned stress is similarly divided between the paper and the gasunder pressure inversely as their permittivities, the permittivity ofthe gas under pressure being about unity but the very high dielectricstrength of the gas under pres sure can safely assume three or four ormore times the stress assumed by the paper without breakdown, andpuncture is thus effectively prevented.

Should, therefore, there be any relatively thin or weakened portions inthe paper, such portions are greatly reinforced by the coactiontherewith of the gaseous dielectric under pressure, the latter acting tocause the weaker or thinner portions of the paper to assume a muchsmaller fraction of the total stress than would otherwise be the case,and thus breakdown and puncture is further prevented.

. To illustrate certain of the unusual results flowing from suchcoaction, it might be pointed out that the dielectric strength of, forexample, dry uncalendered linen paper even of poor stock is increasedabout 350% when made to coact with nitrogen under fifteen atmospheres ofpressure.

Due to this coaction, it is possible to make use of less heavy paper andeven of thinner paper or lesser layers and thus I am enabled further tolessen the space occupied by solid dielectric material and make suchspace available for the reception of the winding.

Furthermore, I achieve other important and new results due to thiscoaction; it is well known that, in a transformer, the capacity betweenturns and between layers and the like should be reduced as much aspossible. A function of the capacity is the character of the dielectricmedium and the higher the permittivity of this me dium the higher is thecapacity. For example, where paper insulation is used with oil, thepermittivity of the resultant dielectric medium is on the order of 4.5;compared to that value, I am enabled, with the combination of paper andgaseous dielectric under pressure, to achieve not only a betterinsulation as such and to lessen the quantity of paper that wouldotherwise be employed, but also to achieve a permittivity on the orderof 2,5 or so. For example, the permittivity of dry uncalendered kraftpaper and nitrogen at fifteen atmospheres pressure is about 2.3. Thusthe condenser or capacity effect is greatly reduced.

It will thus be seen that there has been provided in this invention atransformer construc tion and method of making the same in which thevarious objects hereinabove noted, together with many thoroughlypractical advantages, are successfully achieved.

As many possible embodiments may be made of the mechanical features ofthe above invention and as the art herein described might be varied invarious parts, all without departing from the scope of the invention, itis to be understood that all matter hereinabove set forth or shown inthe accompanying drawings, is to be interpreted as illustrative and notin a limiting sense.

I claim:

1. In transformer construction,l in combination a core having a sleeveof solid dielectric material thereabout and spaced therefrom, aplurality of coil spacers spaced along said sleeve, each spacer having ahub portion and two spaced flanges, the` hub portion extending beyondthe outer face of at least one of said flanges, coils wound betweenspaced spacers and onto said sleeve and the pro jecting portions of saidhubs, and a gaseous dielectric under pressure filling the space betweensaid sleeve and the core and the space between the flanges of eachspacer.

2. In transformer construction, in combination, a core having a sleeveof solid dielectric materia] thereabout and spaced therefrom, aplurality of coil spacers spaced along said sleeve, each spacer having ahub portion and two spaced flanges, the hub portion extending beyond theouter face of at least one of said flanges, coils wound between spacedspacers and onto said `eeve and the projecting portions of said hubs,and a gaseous dielectric under pressure filling the space between saidsleeve and the core and the space between the flanges of each spacer,said coils being wound in layers so that the potential of the innermostlayer is different from the potential of the outermost layer, eachspacer having a channel through which the end of the innermost layer ofthe adjacent coil is passed into the space between the ilanges of thespacci', means connecting adjacent coils and positioned in the spacebetween the flanges of the spacer separating adjacent coils, and agaseous dielectric under pressure filling the space between said sleeveand the core and the space between the flanges of the spacers.

3. A high voltage winding comprising, in con bination, a soliddielectric support, a plurality of winding sections spaced therealong,means cornprising solid dielectric material for insulating from eachother those portions of adjacent coils that are nearest said support,and means comprising solid dielectric material and a gaseous dielectricunder pressure serially related therewith for insulating from each otherthe remaining portions of adjacent coils, the dimension in the directionof dielectric stress of said lastmentioned insulating means being lessthan that of said first-mentioned insulating means.

4. A high voltage winding comprising, in combination, a plurality ofcoils arranged in axial alinement along a solid dielectric support, eachcoil having a lesser dimension in an axial direction where its radius issmallest than where it is of largest radius, solid dielectric materialinterposed between those portions of adjacent coils that are of lesseraxial dimension, and solid dielectric material and a gaseous dielectricunder pressure in series therewith interposed between those portions ofadjacent coils that are of greater axial dimension.

5. A high voltage winding comprising, in combination, a solid dielectricsupport, a plurality of winding sections spaced therealong, meanscomprising solid dielectric material for insulating from each otherthose portions of adjacent coils that are nearest said support, andmeans cornprising two dielectrics in series of different permittilitiesfor insulating from each other' the remaining portions of adjacent coilsand having a lesser dimension in the direction of the dielectric stressthan has said rst-mentioned insulating means.

6. A high voltage winding comprising, in combination, a plurality ofcoils arranged in axial alinement along a solid dielectric support, eachcoil having a lesser dimension in an axial direction where its radius issmallest than where it is of largest radius, solid dielectric materialin terposed between those portions of adjacent coils that are of lesseraxial dimension, and means comprising a plurality of dielectricsserially related and having different permittivities for in.- sulatingthe portions of adjacent coils that are of greater' axial dimension.

7. A high voltage winding comprising, in combination, a plurality ofcoil sections insulated from each other by a plurality of insulatingmeans functioning in parallel, one of said insulating means comprisingsolid dielectric material and the other comprising a plurality ofdielectrics of diilerent permittivities arranged in series, saidlast-mentioned insulating means occupying less space than said soliddielectric insulating means.

8. A high voltage winding comprising, in combination, a plurality ofcoil sections insulated from each other by a plurality of insulatingmeans functioning in parallel, one of said insulating means comprisingsolid dielectric material and the other comprising a plurality of soliddielectric members separated by a dielectric of lower permittivity thanthat of the material of which said members are made.

9. A high Voltage winding comprising, in combination, a plurality ofcoil sections insulated from each other by a plurality of insulatingmeans functioning in parallel, one of said insulating means comprisingsolid dielectric material and the other comprising a pair of spacedsolid dielectric members wlth the intervening space lled with a gaseousdielectric .under pressure.

l0. In transformer construction, in combination, a plurality of spacedseparators 0f solid dielectric material, each separator having a hubportion and spaced flanges, coils in the space between separators, and abuier coil wound in the space between the ilanges of at least one ofsaid separators.

1l. In transformer construction, in combination, a plurality of spacedseparators of solid dielectric material, each separator having a hubportion and spaced flanges, coils in the space between separators,successive coils being connected together and the connections beinglocated in the space between flanges of the spacers.

FRANKLIN S. SMITH.

